Butler University
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College of Liberal Arts & Sciences
2015
Two Hundred Years of Forest Change: Effects of
Urbanization on Tree Species Composition and
Structure
Rebecca W. Dolan
Butler University, [email protected]
Follow this and additional works at: http://digitalcommons.butler.edu/facsch_papers
Part of the Botany Commons, and the Forest Biology Commons
Recommended Citation
Dolan, Rebecca W., "Two Hundred Years of Forest Change: Effects of Urbanization on Tree Species Composition and Structure"
Arboriculture & Urban Forestry / (2015): 136-145.
Available at http://digitalcommons.butler.edu/facsch_papers/659
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136
Dolan: Two Hundred Years of Forest Change
Arboriculture & Urban Forestry 2015. 41(3): 136–145
Two Hundred Years of Forest Change:
Effects of Urbanization on Tree Species
Composition and Structure
Rebecca W. Dolan
Abstract. Despite their importance, the dynamics of urban floras are not well understood and quantitative historical data are rare.
The current study used three data sets for trees in Indianapolis/Marion County, Indiana, U.S., to document change over 200 years
to the original beech-maple forest and to examine future implications of contemporary tree planting efforts in light of these
changes. Data on tree composition and size collected before significant settlement in the early 1800s are compared with recent surveys of trees in remnant natural areas and with trees found on city streets and rights-of-way. All the species recorded in historical
surveys are still present in either remnant natural area forests or among city street trees, but frequencies and sizes have changed and
many additional species are now present. Comparison of the composition of the original forest with current remnants shows a 95%
decline of American beech (Fagus grandifolia), the most common species in presettlement forests. Sugar maple (Acer saccharum) has
more than doubled in number. Silver maple (Acer saccharinum) is the most important street tree, with eight species of non-native
broadleaf trees among the most common on city streets, along with evergreen gymnosperms that are not documented in the presettlement flora. Data for contemporary tree planting efforts in the city show a focus on native species that targets replacement of
species that have declined in frequency, especially oaks, in proportions that should be sustainable. Patterns reported here are likely
representative of those in many forested areas undergoing land conversion and development, so the findings apply to many cities.
Key Words. American Beech; Acer saccharinum; Acer saccharum; Fagus grandifolia; Indiana; Indianapolis; Presettlement Forest; Remnant Forests; Silver Maple; Sugar Maple; Urban Forest; Witness Trees.
The composition of trees in cities is determined by
three major factors. The first is the historical natural
vegetation in which the city developed. This composition is controlled by climate, soils, and geologic
history. The second is the matrix of development of
the built environment and what remnants of natural area remain. For example, a recent study documented that present day oaks, dominant species of
the presettlement forest of Chicago, Illinois, U.S.,
are still found in sites associated with presettlement
forests in the city (Fahey et al. 2012). Two hundred
years of urbanization have not erased the signature
of presettlement patterns of vegetation, patches of
forest in a prairie matrix. The third driver of urban
tree composition is based on human preference:
trees planted in greenspaces and along city streets.
More than 80% of the population of the United
States (U.S. Census Bureau 2015) and more than half
©2015 International Society of Arboriculture
of the global human population (UNFPA 2007) now
live in cities, and so receive the benefits of urban
trees. With cities expected to expand 30% in area
over the next few decades (Seto et al. 2012), even
more people will be affected. Trees are an important
component of urban green infrastructure, providing
significant ecological services. They absorb air pollution, reduce soil erosion and stormwater runoff, and
decrease energy consumption by providing shade
and transpiring moisture, which reduce heat island
effects in cities (Nowak et al. 2010 and references
therein). Urban forests provide wildlife habitat and
contribute to biodiversity. The benefits of trees go
beyond improvement of the physical environment.
Trees make an economic impact by increasing property values. Trees contribute to sense of well-being
and provide psychological value beyond utilitarian
services (Dwyer et al. 1991). As urban populations
Arboriculture & Urban Forestry 41(3): May 2015
swell, greenspace and green places in cities will provide for most people’s contact with nature. However,
despite their environmental importance and the large
amounts of money spent to maintain them, there is
still much that is not known (Nowak et al. 2010).
Although the urban forest composition of all cities have been shaped by these three factors, there
are few cities for which data exist to allow comparison and quantification of preurban forest species
composition and structure with current conditions.
Having such data would allow for informed selection of trees for current planting programs that
reflect species historically present—in terms of
composition and relative frequency. To the extent
practical, a focus on plantings that recreate historical forest have the potential to promote biodiversity
across the spectrum of urban biota that rely on trees.
These data do exist for the City of Indianapolis, Indiana, in the American Midwest. Indianapolis is the thirteenth largest city in the United States
and is a state capital. It was founded in a sparsely
populated area in 1820, not by settlers, but by a
proclamation of the U.S. Congress (Bodenhamer
and Barrows 1994). The land on which the city
was developed was surveyed by the federal government around the time Indianapolis was founded,
as part of the opening of the Northwest Territory. Witness trees were identified to species and
their sizes recorded as the land was surveyed.
This paper compares these historical records
with recent data on trees collected from remnant
natural areas and with inventories of street trees
in the city. Objectives were to document how
tree composition and size have changed over 200
years and to examine the implications of contemporary tree planting efforts in light of these
changes. Patterns reported here are likely representative of those in many forested areas undergoing land conversion and development, putting
numbers on trends that apply to many cities.
MATERIAL AND METHODS
Natural Region Setting and History
of Indianapolis
Indianapolis is located in Marion County, Indiana,
in the center of the state. The city and the county
are the same governmental unit, and so occupy
the same geographic space, referred to as India-
137
napolis in this paper. Indianapolis has an estimated
900,000 people in a total area of 105,200 hectares,
a very high human population density of 3,557/
km2 by United States standards (City Data 2015).
The city is located in the Central Till Plain Section of the Central Till Plain Natural Region
(Homoya et al. 1985). Topographically, there is
little relief except where streams cut into unconsolidated glacial till. Historical records and soil
survey records indicate Indianapolis was almost
entirely forested in pre-European presettlement
times (Barr et al. 2002), with remaining land cover
being open water or prairie. Mesic upland forest, mostly beech-maple association (Potzger et
al. 1956), covered 76% of the county, with small
areas of drier upland forest on ridges. Wet-mesic
depressional forests were scattered throughout the
county with floodplain forests along major rivers
and tributaries. These forests were reduced to 13%
cover by the late 1900s (Barr et al. 2002). Remaining forest cover is found in remnant natural areas
and scattered woodlots, usually along streams in
areas too wet or steep for farming (Brothers 1994).
Logging and grazing likely occurred on these sites.
Sources of Data
Three sources of tree data were analyzed for this
study. Two are culled from previously published
studies. Historical data from the 1820 General
Land Office surveys for Marion County were transcribed from original records and summarized
in Barr et al. (2002). Detailed individual tree size
(e.g., diameter, assumed to be diameter at breast
height, DBH) data were provided by the lead author of that paper for this current study; the dataset is referred to as “historical.” Current street
tree species and sizes are from a forest resource
analysis prepared for the City of Indianapolis by
Peper et al. (2008). Finally, original to this paper,
current tree composition in remnant natural areas
in the city is presented, based on transect sampling
conducted at five sites. All three sources provide
data on individual tree identities and diameters.
Forest inventory data are also available for Marion
and other counties in the United States through the
USDA Forest Service Forest Inventory and Analysis
Program (USDA FIAP 2015). This program now uses
remote sensing combined with a sample of groundtruthed field plots to evaluate forest health annually.
©2015 International Society of Arboriculture
138
Data estimated include species composition and
size class. Percent sample errors of >50% associated with estimates for Marion County precluded
use of detailed data from the program in this paper.
Historical Data
The area that is now Indianapolis was surveyed by
the General Land Office of the federal government
from 1820 to 1822. Surveyors generally walked
the perimeter of each square-mile section, recording the diameter and name of two or more witness trees at the intersection of each section and
quarter section line. Although there is potential
for bias in the choice of each tree serving as a witness tree, such as in favor of those of economic
value or those whose bark is easy to mark, prior
studies have not found evidence of systematic bias
(Bourdo 1956; Radeloff et al. 1999). These General
Land Office Survey records provide the best primary account of presettlement vegetation in Indiana (Barr et al. 2002). Although witness trees represent relatively few individual trees of the original
forest, to the extent they were randomly selected
they do accurately reflect percentage relationships between species present (Blewett and Potzger
1951) and provide quantitative information of species present at a particular point in time (Schulte
and Mladenoff 2001; Vellend et al. 2013). Barr et
al. (2002) provide a summary of transcribed survey notebooks for Marion County. They matched
common names used by surveyors with currently used names. Their original transcribed data
provide the historical data for the current study,
3,620 individual trees from 31 different species.
Recent – Remnant Natural Areas
Tree composition data for extant remnant natural
areas in Indianapolis is based on pooled data from
five sites sampled from 2003 to 2007 (Table 1). All
sites are forested. Three of the five sites—Spring
Pond Nature Preserve, Eagle’s Crest Nature Preserve, and Woollen’s Gardens—were recognized
in 1994 as being the best extant examples of what
presettlement forests were like (Brothers 1994).
Two different sampling protocols were used. Two
sites were sampled using 100 m2 circular plots arrayed in a three × three grid of plot centers separated by 20 m for a total of nine plots per grid (=
grids method) (Table 1). All trees greater than 7.5
©2015 International Society of Arboriculture
Dolan: Two Hundred Years of Forest Change
cm DBH were identified and their diameters recorded. At an additional three locations, point-quarter
method sampling was used to quantify the vegetation present (= p-q method). Every 10 m along a
100 m transect, four trees were identified and their
DBH recorded. Each transect therefore yielded data
on 40 trees. These studies together yielded data
on a total of 1,602 individual trees and their sizes.
Table 1. Natural remnants inventoried in recent years in
Indianapolis, Indiana, U.S.
Site
Art and Nature Park
Eagle’s Crest Nature
Preserve
Southwestways Park
Spring Pond Nature
Preserve
Woollen’s Garden Park
Year Size
inventoried (ha)
2005
24
2007
120
Sample No. transects
method or grids
p-q
5
grids
8
2004
2007
36
18
p-q
grids
2003
15
p-q
10
8
7
Street Trees
The City of Indianapolis maintains a database of
trees on public rights-of-way. The database was
compiled and analyzed as part of a 2008 cost-benefit analysis. The analysis addressed whether the
accrued environmental benefits, such as energy
savings and stormwater runoff reduction, and economic benefits, such as property value increase,
from Indianapolis’ street trees, justify the annual
expenditures associated with them (e.g., tree planting, maintenance, agency administrative costs)
(Peper et al. 2008). Some trees in the rights-of-way
are naturally established remnants of the original forest, others have been planted. Species and
DBH class data for 101,311 trees from that 2008
report comprise the street tree data in this study.
Data Analysis
Data from the three data sources were compiled to document change in tree size and composition over the last 200 years. Attention was
paid to developing an analysis scheme that acknowledged the limitations associated with
each data type (e.g., lack of information on
density). Where trees were identified only to
genus in the historical data, species were similarly lumped for the other two data sources.
Importance integrates both numbers of individuals and size to provide a measure of how
relatively predominant each species is. Impor-
Arboriculture & Urban Forestry 41(3): May 2015
tance for street trees are those values reported in
Peper et al. (2008), calculated as the mean of the
relativized frequency, leaf area, and canopy cover
estimate for each species. Leaf area and canopy
cover data were not available for historical and
recent natural area trees, and so importance
was calculated by adding frequency and relativized mean DBH for each species and dividing
by two. The two methods for calculating importance are not directly comparable but provide a
measure of which trees are most predominant in
terms of both number and size in each data set.
The distribution of trees among size classes for
the most common species was graphed to compare
forest composition through time for all three data
sources. This approach, analyzing tree size based on
size class ranges rather than individual tree sizes,
reduces some sources of error potentially associated with individual diameter values recorded in
the General Land Office Surveys (see discussion
in Schulte and Mladendoff 2001). Size infers age
of tree and reproductive health of populations.
RESULTS
Comparing and Historical and
Recent Trees
The last 200 years have seen a change in tree
composition in Indianapolis as the city has developed. Although all but five species (occurring
in frequencies of less than 1%) identified during
historical land surveys are still found in remnant
natural areas in Indianapolis, the frequencies of
some of the most common species have shifted
significantly (Table 2). The most common species
in presettlement forests, American beech (Fagus
grandifolia), declined as a percentage of total trees
by 95%. Two species, each representing 11% of the
original forest, now have divergent patterns: sugar
maple (Acer saccharum) has more than doubled in
frequency, while white ash (Fraxinus americana)
has declined to less than 1% of trees present. White
oak (Quercus alba) has declined from 6% to 1%.
Native elms (Ulmus spp.) have increased the most
through time as a percentage of all trees, increasing
almost five-fold from 5% of witness trees to 23%
of trees in current natural areas. Boxelder (Acer
negundo) and hickories (Carya spp.) changed in
composition by less than 3% between the record-
139
ed periods. Twenty-two other species were present in very low numbers at both points in time.
The largest trees, based on mean DBH in the
presettlement forests, were tulip popular (Liriodendron tulipifera), sycamore (Platanus occidentalis), various oak species, black walnut (Juglans
nigra), and blue ash (Fraxinus quadrangulata).
Tulip poplar, sycamore, and oak continue to be
among the largest trees in Indianapolis’ forests,
while the mean size of black walnut and blue ash
has declined. Cottonwood (Populus spp.) is the
only species to nearly double in mean size (Table 2).
Street Trees
Street trees differ in composition from those in
presettlement forests and in current natural areas
in Indianapolis. All species recorded in historical
surveys are present in street tree inventories, except one, black willow (Salix nigra). The difference
comes with the addition of species not found in
presettlement forests. Eight species of non-native
broadleaf trees are among the most common in
number on city streets (Table 2). Only one, tree of
heaven (Ailanthus altissima), occurred in recent
samples from natural areas. An additional group
of non-native trees, evergreen gymnosperms, account for 10% of all street trees. The most common native street trees were silver maple, sugar
maple, hackberry (Celtis occidentalis), and white
ash. The most numerous non-natives were crabapple (Malus spp.) and white mulberry (Morus alba).
Similarities of Species Composition
in Data Sources
Based on the species presented in Table 2 (all species in historical and recent studies and street trees
present at 5% frequency or greater), Jaccard’s similarity of species composition between trees recently
surveyed in remnants and those from the historical
record is 66%, while street trees are only 28% similar
to trees from the historical record, highlighting the
difference in street tree composition compared with
trees historically present in Indianapolis. Trees in
remnants have a similarity of 41% with street trees.
Importance
Importance values document the decline of
American beech and the increase of sugar ma-
©2015 International Society of Arboriculture
140
Dolan: Two Hundred Years of Forest Change
Table 2. Frequency and mean diameter at breast height (DBH) for trees in historical and recent datasets, along with street
trees present at 5% frequency or greater. Frequency values of greater than five are in bold. Historical data are from Barr
et al. (2002). Most common street tree data are from Peper et al. (2008).
Species
Common name
Acer negundo
Boxelder
Acer nigrum
Black maple
Acer saccharinum
Silver maple
Acer saccharum
Sugar maple
Aesculus glabra
Ohio buckeye
Betula nigra
River birch
Carpinus carolinianaMusclewood
z
Carya spp. Hickory spp.
Celtis occidentalis Hackberry
Cornus florida
Flowering dogwood
Crataegus spp.
Hawthorne
Fagus grandifolia
American beech
Fraxinus americana
White ash
Fraxinus pennsylvanica
Green ash
Fraxinus quadrangulata
Blue ash
Gleditsia triacanthos
Honeylocust
Juglans cinerea
Butternut
Juglans nigra
Black walnut
Liriodendron tulipifera
Tulip poplar
Ostrya virgiana
Hophornbeam
Platanus occidentalis
Sycamore
Populus grandidentata
Bigtooth aspen
Populus deltoides
Cottonwood
Quercus alba
White oak
Quercus rubra
Red oak
Quercus velutina
Black oak
Other oaks Quercus spp.y
Salix nigra
Black willow
Salix spp.
Willow
Tilia americana
Basswood or linden
Ulmus spp.x
Elm spp.
Acer rubrum
Red maple
Ailanthus altissimaw
Tree of heaven
Cercis canadensis
Redbud
Diospyros virginiana
Persimmon
Fraxinus profunda
Pumpkin ash
Maclura pomiferaw
Osage-orange
Morus albaw
White mulberry
Prunus serotina
Blackcherry
w
Robinia pseudoacacia Black locust
Sassafras albidum
Sassafras
Ulmus pumilaw
Siberian elm
Gymnosperm spp.w
Gymnosperms
w
Acer platanoides Norway maple
Catalpa speciosaw
Northern catalpa
Liquidambar styracifluaw
Sweetgum
Malus spp.w
Crabapple
Prunus spp.
Plum
Pyrus calleryanaw
Callery pear
Historical
Recent remnants
% of trees Mean DBH (cm)
% of trees Mean DBH (cm)
525
824
<1
20
3
24
<1
33
531
1138
2613
<1
10
3
11
<1
40
-
-
1 15
<1 5
7 35
420
338
519
<1
10
<1
5
<1
20
<1
9
40 38
233
11 40
<134
<1
35
2
31
<1
50
<1
10
<1 30
131
<1
25
-
-
2
53
2
30
1
68
1
68
1 15
<124
1 68
162
<1
14
-
-
1 30
158
6 58
153
1
50
1
67
1
60
<1
45
<1
60
2
42
<1
48
-
-
<1
18
-
-
1
33
1
28
543
2314
-
-
<1
15
-
-
<1
13
-
-
<1
12
-
-
<1
30
-
-
<1
16
-
-
<1
23
-
-
<1
20
-
-
2
20
-
-
2
37
-
-
<1
4
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
Street trees
% of trees
1
<1
15
6
<1
<1
<1
1
6
2
1
<1
5
2
<1
2
<1
1
1
<1
1
<1
2
<1
2
<1
2
1
<1
<1
2
1
2
<1
<1
<1
3
2
1
<1
4
10
3
1
1
4
1
1
Carya cordiformis (bitternut hickory), C. glabra (pignut hickory), C. laciniosa (shellbark hickory), and C. ovata (shagbark hickory).
Quercus macrocarpa (bur oak), Q. michauxii (swamp white oak), Q. muehlenbergii (chinquapin oak), and Q. palustris (pin oak).
x
Ulmus americana (American elm), U. thomasii (rock elm), and U. rubra (slippery elm).
w
Not native to Indianapolis/Marion County.
z
y
ple and elm over time in extant remnants compared to historic forests in Indianapolis (Table
2). Comparing historical data with recent data
from remnant forests shows American beech
declined by almost 90% while sugar maple and
elm almost doubled in importance. American beech, white ash, sugar maple, white oak,
©2015 International Society of Arboriculture
hickory, and elm dominated original forests.
In current remnant forests, sugar maple and
elm species dominate, with boxelder the only
other species with an importance of five or
greater. The decline in dominance of American beech with time is replaced largely by small
increases in importance of many other trees.
Arboriculture & Urban Forestry 41(3): May 2015
141
Silver maple is the predominant street
tree, with 25% importance. Sugar maple,
hackberry and white ash are other species with importance values greater than five.
Size Class Distributions
Size distribution of American beech has shifted
from 60% of stems being in the smallest three
size classes historically to a more even distribution with no size class having over 20%
of stems (Figure 1). Sugar maple has had a reverse trend, with stems in the two smallest
size classes increasing 18%. Elm has similarly
experienced a large increase in the percentage of trees in the smaller size classes in recent remnants, compared to historical records.
Because street trees do not have natural recruitment patterns due to growing
in managed environments, shapes of size
class distribution curves are not informative of reproductive success, but they do offer
insight into likely future population structure.
Sugar maple and elm are likely to increase
in predominance while beech will decline
based on size class distribution (Figure 1).
DISCUSSION
Tree species composition in Indianapolis has
changed with 200 years of habitat conversion
and urbanization. Although all the species
recorded in historical surveys are still present in either remnant natural area forests or
among city street trees, proportions and sizes
have changed and many additional species are
now present. There has been a large decline
in American beech with an increase in sugar
maple. Data in the USDA Forest Service Forest
Inventory and Analysis Program (USDA FIAP
2015) for trees on forest land (land at least 10%
stocked by trees, including land formerly covered by trees and naturally regenerating) and
timberland (forest land that is producing or
is capable of producing forest crops of industrial wood) in Indianapolis (FIDO) based on
119 plots, confirm the trends reported in this
paper. For example, from 2003 to 2013, sugar
maple increased as a percentage of total estimated trees from 18% to 27%, with increases
concentrated among the smallest trees. The
Figure 1. Frequency histogram of size distribution (DBH): a)
sugar maple (Acer saccharum), b) American beech (Fagus
grandifolia), and c) elm (Ulmus spp.) species trees from
three different data sources in Indianapolis, Indiana. Size
classes: 1 = 7.6–15.2 cm (3–6 inches), 2 = 15.2–30.5 cm (6–12
inches), 3 = 30.5–45.7 cm (12–18 inches), 4 = 45.7–61.0 cm
(18–24 inches), 5 = 61.0–76.2 cm (24–30 inches), 6 = 76.2–
91.4 cm (30–36 inches), 7 = 91.4–106.7 cm (36–42 inches),
8 = >106.7 cm (>42 inches). All size classes were scaled in
inches due to street tree data only being reported in inch
interval size classes in the street tree data source (Peper
et al. 2008).
©2015 International Society of Arboriculture
142
percentage of sugar maple in the smallest size
classes (2.5 to 15 cm) increased from an estimated 22% to 33% to all trees in these classes.
The decline of American beech is likely
explained in part by the loss of beech-maple forest through direct habitat destruction or conversion. Seventy-six percent of the county was
covered by beech-maple forest in presettlement
times (Barr et al. 2002). Upland forest was preferentially cleared for agriculture in the early part
of the 19th century (Brothers 1994), which is
reflected in the current estimated remaining forest cover in the county of 13% (Barr et al. 2002).
Additional factors that may have contributed to the decline of American beech in Marion
County include poor tolerance of disturbance
(especially disturbance to its shallow roots), compacted urban soil, low preference in the landscape
industry due to its not doing well as ball-andburlap stock, and the fact that its smooth bark is
subject to vandalism in street and park settings
(Carrie Tauscher, urban forester, Indiana Department of Natural Resources pers. comm.). It should
also be noted that American beech frequency
may have been overstated in the historical surveys. This species may have been preferentially
selected for witness trees due to its smooth bark
which would have been easy to blaze and mark.
The species shifts observed in Indianapolis may
also be due in part to larger regional changes.
Increasing presence of sugar maple and decline
of American beech was noted in Indiana as early
as 1977 (Abrell and Jackson 1977). The increase
in sugar maple has been attributed to release
from competition with American beech and
alteration of natural fire regimes (USDA 2006).
Decreased fire favors fire-sensitive species like
sugar maple. The large proportion of small sugar
maples in Indianapolis suggests the species will
continue to increase in importance. As it becomes
more dominant, sugar maple can have a cascading effect, further influencing forest composition through secondary effects, including altered
nitrogen cycling (Lovett and Mitchell 2004).
Recent surveys also support a large increase
in elm species, an increase in frequency from 5%
to 23%, compared with historical records. Native
elms may be any of three species, American elm
(Ulmus americana), rock elm (U. thomasii), or
©2015 International Society of Arboriculture
Dolan: Two Hundred Years of Forest Change
slippery elm (U. rubra). Dutch elm disease, introduced in the 1950s in Indiana, killed almost all large
elms. Natural populations have rebounded in some
areas, but the disease still kills larger, older trees.
Size of elm has decreased from a mean DBH of 43
cm to 14 cm in current remnants. Street tree elms
include non-native Siberian elm (Ulmus pumila).
Blackcherry (Prunus serotina) was not
reported in the historical data. This may be
because of its extremely flaky bark, which is hard
to mark and it might have been avoided by surveyors. It may also be that as a fast-growing tree
of forest openings, it has become much more
common with the forest disturbance that accompanied settlement and urbanization. Interestingly, Sassafras, the most common tree in urban
forests in a recent statewide study (Nowak et
al. 2007), and another fast-growing tree of species of forest openings, was not recorded in historical surveys and was very rarely encountered
in recent surveys in natural remnant woods.
Boxelder, a fast-growing disturbance-tolerant
species, remained of similar low importance.
Cottonwoods, the trees with the largest
increase in mean size between historical surveys and current remnants, are primarily found
along streams and creeks and in floodplain forests
bordering streams and creeks. Many of the remnant patches of this habitat type in Indianapolis
are now protected as parks. The increase in tree
size may be due to protection from disturbance.
The most striking difference between urban
street tree composition and that of historical or
current natural woods is the large percentage of silver maple. Its predominance has increased almost
thirty times over presettlement values. In Chicago,
dominance of silver maple has increased an amazing 80,000 percent over the same recorded period
(Fahey et al. 2012). This species was often a street
tree of choice in the 20th century because of its fast
growth. It is not recommended for planting in urban
forests in Indiana (IDNR 2015) because its quick
growth makes it weak and susceptible to damage in
wind and ice storms. The species is not among those
currently being planted on city streets (Table 3).
Although all trees recorded in the historical survey records are found among Indianapolis’ street
trees, many other species are now planted in the
city. The proportion of importance represented by
Arboriculture & Urban Forestry 41(3): May 2015
other species, where species in the original forest
once grew, has greatly increased. Evergreen gymnosperms, none present in presettlement Indianapolis, with the possible exception of red cedar
(Juniperus virginiana), comprise 10% of street
trees. These data show that human preference has
greatly altered the tree composition of Indianapolis. Shifts in dominance from native species, such
as oaks, to smaller-statured, shorter-lived nonnative species have been reported for the urban
forests of Chicago, with associated loss of ecosystem service over time predicted (Fahey et al. 2012).
The Future
The non-profit beautification group Keep Indianapolis Beautiful (KIB) is partnering with the
city to plant 100,000 trees. The choice of species
planted will be the greatest opportunity humans
have to directly influence the future of Marion
County’s urban tree composition. Records of recent plantings show native trees are the most commonly selected, with over 20% of 12,174 trees
planted since 2008 being species of oaks (Table 3).
Oaks have declined in the county since presettlement times. Species of depressional ponds and
seasonally flooded wetlands, like swamp white oak
(Quercus bicolor) and bur oak (Q. macrocarpa), have
had their habitats drained. Oaks planted in urban
spaces will replace an all but lost component of
the native forest, providing wildlife with food and
habitat. Oaks in the eastern United States provide
significant ecological services as one of the best
food sources for birds and other desirable wildlife that feed on insects (Burghardt et al. 2009).
Although slightly more than 20% of trees
planted by KIB are oaks, no single species comprises more than 10% of the total. For sustainability in an urban forest, Santamour (1990)
recommends no single species should be more
than 10% of trees planted in a given area, and
no genus more than 20%. KIB’s planting list
also follows the recommendation of Peper et al.
(2008), for Indianapolis to plant non-maples.
Natural forces that will continue to influence
forest composition on a landscape scale include
additional introduced pests. The emerald ash
borer (Agrilus planipennis Fairmaire) (EAB), a
coleopteran beetle, was recently introduced and
is spreading in the county (Purdue Univ. Exten-
143
sion 2015). Ashes have declined from approximately 12% of all trees in historical surveys, to
around 3% in recent surveys, before the arrival
of the EAB. It is predicted all untreated trees will
die. Ashes comprise about 7% of street trees.
Streetscape tree selection is influenced by
many factors, including availability, price, aesthetics, species’ viability in the urban environment, and cost of maintenance. To the extent
native species can be chosen while weighing
these factors, urban trees can increase biodiversity of associated flora and fauna (Ikin et
al. 2012) in cities while promoting regional
distinctness and countering biotic homogenization. However, a caveat looking into
the more distant future, is that as tree species distributions are shifted by global climate
change, historical species composition may
become less relevant as baseline condition data.
Table 3. Trees planted in Indianapolis by Keep Indianapolis Beautiful (2008–2011).
Species
Common name
Quercus macrocarpa
Bur oak
Quercus bicolor
Swamp white oak
Cercis canadensis
Redbud
Amelanchier × grandifloraServiceberry
Quercus rubra
Red oak
Quercus muehlenbergii
Chinquapin oak
Gymnocladus dioicus
Kentucky coffeetree
Liquidambar styraciflua Sweetgum
Juniperus virginiana
Red cedar
Acer saccharum
Sugar maple
Ulmus americana
American elm
Nyssa sylvatica
Black gum
Acer rubrum
Red maple
Amelanchier sp.
Serviceberry species
Quercus sp.
Oak species
Qty.
% total
774
6.4
745
6.1
5924.9
520 4.3
416
3.4
415
3.4
407
3.3
3873.2
383
3.1
377
3.1
368
3.0
336
2.8
323
2.7
319
2.6
255
2.1
CONCLUDING REMARKS
With an estimated annual loss of urban tree cover,
a proxy for overall urban forest resources, of
0.9% in the United States (Nowak and Greenfield
2012), threats to urban trees continue. Information on how urban forests are changing is needed
to better inform policies to “protect, sustain and
enhance urban forests health and benefits for
future generations” (Peper et al. 2008). Although
it does not include data for trees in backyards or
other private property (those data do not exist
for Indianapolis and likely never will due to
property owners’ rights), this study provides a
snapshot of tree composition in Indianapolis, allowing a degree of quantification of the current
©2015 International Society of Arboriculture
144
Dolan: Two Hundred Years of Forest Change
fingerprint of human alteration of forests in the
city. Patterns reported here are likely representative of those in many forested areas undergoing land conversion and development, so the
findings apply to many cities. The quantitative
data presented here provide baseline numbers
to which the future urban forest of Indianapolis
can be compared and which can be used for statistical comparisons with data from other cities.
Acknowledgments. Witness tree data were supplied by Bob Barr,
Center for Earth and Environmental Sciences, Indiana University
Purdue University, Indianapolis. The Indianapolis Parks Department Office of Land Stewardship funded the recent inventories of
natural areas. Thanks to Don Miller of Indy Parks for encouraging
and facilitating urban botanical research in Indianapolis. Marian
Moore and many Butler University undergraduates assisted with
field work. Burney Fisher and Carrie Tauscher made valuable comments that improved earlier manuscript drafts.
LITERATURE CITED
Abrell, D.B., and M.T. Jackson. 1977. A decade of change in an
old-growth beech-maple forest in Indiana. American Midland
Naturalist 98:22–32.
Barr, R.C., B.E. Hall, J.A. Wilson, C. Souch, G. Lindsey, J.A. Bacone,
R.K. Campbell, and L.P. Tedesco. 2002. Documenting changes
in the natural environment of Indianapolis-Marion County
from European settlement to the present. Ecological Restoration 20:37–46.
Blewett, M.B., and J.E. Potzger. 1951. The forest primeval of Marion and Johnson counties, Indiana, in 1918. Butler University
Botanical Studies 10:40–52.
Bodenhamer, D.J., and R.D. Barrows. 1994. The Encyclopedia of
Indianapolis. Indiana University Press, Bloomington, Indiana,
U.S. 1600 pp.
Bourdo, E.A. 1956. A review of the General Land Office Survey
and of its use in quantitative studies of former forests. Ecology
37:754–768.
Brothers, T.S. 1994. Flora and Fauna. pp. 583–585. In: D.J. Bodenhamer and R.D. Barrows (Eds.). The Encyclopedia of Indianapolis, Indiana University Press, Bloomington, Indiana, U.S.
Burghardt, K.T., D.W. Tallamy, and W.G. Shriver. 2009. Impact of
native plants on bird and butterfly biodiversity in suburban
landscapes. Conservation Biology 23:219–224.
City Data. 2015. <www.city-data.com>
Dwyer, J.F., H.W. Schroeder, and P.H. Gobster. 1991. The significance of urban trees and forests: toward a deeper understanding
of values. Journal of Arboriculture17:276–284.
Fahey, R.T., M.L. Bowles, and J.L. McBride. 2012. Origins of the
Chicago urban forest: Composition and structure in relation to
presettlement vegetation and modern land use. Arboriculture &
Urban Forestry 38:181–193.
Homoya, M.A., D.B. Abrell, J.R. Aldrich, and T.W. Post. 1985. Natural
Regions of Indiana. Proceedings of the Indiana Academy of
Science 94:245–268.
IDNR (Indiana Department of Natural Resources). 2015. Community & Urban Forestry. <www.in.gov/dnr/forestry/2854.htm>
©2015 International Society of Arboriculture
Ikin, K., E. Knight, D.B. Lindenmayer, J. Fischer, and A.D. Manning.
2012. The influence of native versus exotic streetscape vegetation
on the spatial distribution of birds in suburbs and reserves. Diversity and Distributions <doi:10.1111/j.1472-4642.2012.00937.x>
Lovett, G.M., and M.J. Mitchell. 2004. Sugar maple and nitrogen
cycling in the forests of eastern North America. Frontiers in
Ecology and the Environment 2:81–88.
Nowak, D.A., and E.J. Greenfield. 2012. Tree and impervious cover
change in U.S. cities. Urban Forestry & Urban Greening 11:21–30.
Nowak, D.J., A.B. Cumming, D.B. Twardus, R. Hoehn, and M. Mielke. 2007. Monitoring Urban Forests in Indiana: Pilot Study 2002.
National Forest Health Monitoring Program. NA-FR-01-07.
U.S. Department of Agriculture, Forest Service, Northern Research Station, Newtown Square, Pennsylvania, U.S. 13 pp.
Nowak, D.J., S.M. Stein, P.B. Randler, E.J., Greenfield, S.J. Comas,
M.A. Carr, and R.J. Alig. 2010. Sustaining America’s Urban
Trees and Forests: a Forests on the Edge Report. General Technical Report NRS-62. U.S. Department of Agriculture, Forest
Service, Northern Research Station, Newtown Square, Pennsylvania, U.S. 27 pp.
Peper, P.J., E.G. McPherson, J.R. Simpson, K.E. Varga, and Q. Xiao.
2008. City of Indianapolis, Indiana municipal forest resource
analysis. Technical report to: Indy Parks and Recreation Department, City of Indianapolis, Indiana. Center for Urban Forest Research, USDA Forest Service, Pacific Southwest Research
Station, Davis. 68 pp.
Potzger, J.E., M.E. Potzger, and J. McCormick. 1956. The forest primeval of Indiana as recorded in the original U.S. land surveys
and an evaluation of previous interpretations of Indiana vegetation. Butler University Botanical Studies 13:95–111.
Purdue University Extension. Emerald Ash Border in Indiana.
<http://extension.entm.purdue.edu/EAB/index.php?page=ident/
eab>
Radeloff, V.C., D.J. Mladenoff, H.S. He, and M.S. Boyce. 1999. Forest landscape change in the northwestern Wisconsin Pine Barrens from pre-European settlement to the present. Canadian
Journal of Forestry Research 29:1649–1659.
Santamour, F.S. 1990. Trees for urban planting: diversity, uniformity
and common sense. pp. 57–65. In: Proceedings of the 7th Conference of Metropolitan Tree Improvement Alliance (METRIA),
The Morton Arboretum, Lisle, Illinois, U.S.
Schulte, L.A., and D.J. Mladenoff. 2001. The original US Public
Land Survey records: Their use and limitations in reconstructing presettlement vegetation. Journal of Forestry 99:5–10.
Seto, K.S., B. Güneralp, and L.R. Hutyra. 2012. Global forecasts of
urban expansion to 2030 and direct impacts on biodiversity and
carbon pools. Proceedings of the National Academy of Science
<doi:10.1073/pnas.1211658109>
U.S. Census Bureau. 2015. <www.census.gov/geo/www/ua/uafaq.
html>
UNFPA. 2007. State of the World Population 2007: Unleashing the
Potential of Urban Growth. United Nations Population Fund,
New York City, New York, U.S. 108 pp.
USDA FIAP. 2015. <http://www.fia.fs.fed.us>
USDA. 2006. Plant guide: sugar maple. <http://plants.usda.gov/
plantguide/pdf/pg_acsa3.pdf>
Vellend, M., C.D. Brown, H.M. Kharouba, J.L. McCune, and I.H.
Myers-Smith. 2013. Historical ecology: Using unconventional
data sources to test for effects of global environmental change.
American Journal of Botany 100:1294–1305.
Arboriculture & Urban Forestry 41(3): May 2015
145
Rebecca Dolan
Friesner Herbarium
Butler University
4600 Sunset Ave.
Indianapolis, Indiana 46208, U.S.
[email protected]
©2015 International Society of Arboriculture